Magnetic disk and magnetic recording/reproduction apparatus

ABSTRACT

A lubricating film is provided for a magnetic disk having a data region and a CSS region formed on its surface. The lubricating film ensures low stiction and good resistance to contact sliding in the data region and also ensures good CSS durability in the CSS region. Therefore, it is possible to provide a magnetic disk and a magnetic recording/reproducing device which do not cause problems with sliding between the magnetic head and the magnetic disk while the apparatus is running normally and even when the apparatus stops accidentally. The lubricating film formed in the data region of the magnetic disk is firmly fixed to the surface of the magnetic disk and is hardly liable to stiction. In addition, it is thick enough to ensure good durability even in the case of contact sliding. The lubricating film formed in the CSS region is composed of a lubricant which is firmly fixed to the surface of the magnetic disk and another lubricant which is weakly fixed to the surface of the magnetic disk; therefore, it is superior in CSS durability. This contributes to the highly reliable magnetic disk and magnetic recording/reproducing device.

TECHNICAL FIELD

The present invention relates to a magnetic disk and a magneticrecording/reproducing device and, more particularly, to a magnetic diskand a magnetic recording/reproducing device characterized by a highrecording density.

BACKGROUND OF THE INVENTION

The continuing development of the magnetic recording/reproducing deviceof the hard disk type is following the trend toward reduction in thediameter of the magnetic disk, reduction in the size and weight of theapparatus, and an increase in recording density. The higher therecording density of the magnetic disk becomes, the smaller is thedistance (or flying height) between the magnetic disk and the magnetichead. It is expected in the near future that recording and reproducingwill be accomplished in such a manner that the magnetic head is incomplete contact with the magnetic disk. Then, the magnetic disk will besubject to a much severe sliding condition. On the other hand, anincrease in recording density needs a smaller flying height and asmoother magnetic disk surface (for stable flying). The consequence isthat the head slider (supporting the magnetic head) slides on (keepingin contact with) the magnetic disk for a longer period of time thanbefore (sliding in this manner is referred to as contact slidinghereinafter), the disk is subject to more dynamic friction and wear thanbefore during its start-up, and there occurs a limiting static friction(referred to as stiction hereinafter) between the head and the disk. Theresult of an increase in the dynamic friction and wear due to contactsliding is an occasional disk crash and head wear which tends to disablerecording and reproducing operations. Moreover, strong stiction disablesthe start-up of the disk and damages the disk head.

In order to address the above-mentioned problems, there has beendeveloped a magnetic disk of a new type which has two separate regions:one in which the head slider stands by when the magnetic disk is at restand experiences contact start and contact stop when the disk starts andstops, and the other in which the head performs recording andreproducing while the disk is running. The former region is referred toas CSS region and the latter as a data region. The CSS region is usuallyformed in an inner section of the magnetic disk and it has its surfaceroughened so as to prevent stiction. By contrast, the data region hasits surface smoothed so as to ensure a stable head floating. Themagnetic disk having a CSS region and data region needs a speciallubricating film and lubricating technologies. For example, JapanesePatent Laid-open No. 36277/1994 discloses a method of preventingstiction by forming a protuberance (about 5 nm high) on the rail surfaceof the slider in the CSS region. Also, Japanese Patent Laid-open No.111292/1994 discloses the use of a liquid lubricant in the CSS regionand a solid lubricant in the data region. These prior art technologiesare directed to the lubricating film to be applied to the magnetic diskin which are formed the CSS region and data region, and the lubricatingfilm realizes to some extent the sliding characteristics required of theCSS region and data region. There is a distinct difference inrequirements between the lubricating film for the CSS region and thelubricating film for the data region because the head-disk sliding statediffers in these two regions. In the CSS region, it is possible tosomewhat reduce stiction by roughening the surface of the magnetic disk,but there is a need for a lubricating film with good durability becausecontact sliding takes place when the disk starts up and stops. In thedata region, however, it is necessary that the disk have a small surfaceroughness and the lubricating film have a low stiction. The reason forthis is that the head slider could come into contact with the dataregion (causing strong stiction) when the disk stops suddenly (due tosome anomaly) while the head slider lies in the data region. Therefore,the lubricating film in the CSS region should differ in lubricatingperformance from that in the data region.

The lubricant now in use for magnetic disks is a perfluoropolyethercompound having functional groups for adsorption to the disk surface.This lubricant gives rise to a lubricating film which is composed of alayer firmly adsorbed to the disk surface and a layer which is adsorbedweakly or not adsorbed to the disk surface. The firmly adsorbedlubricating layer does not separate from the disk surface when the diskis washed with a perfluorocarbon solvent. On the other hand, the weaklyadsorbed lubricating layer is easily separated from the disk surface bywashing. This weakly adsorbed lubricating layer, however, plays animportant role in the CSS region which needs good durability, because itis necessary that the lubricant partly moves to the slide surface of thehead slider at the time of sliding so that a stable frictional state isestablished. Without this weakly adsorbed layer in the CSS region, it isimpossible to maintain satisfactory reliability. By contrast, the dataregion needs low stiction, because cohesion of the lubricant in the gapbetween the head and the disk should be avoided when the head comes intocontact with the data region at the time of an anomalous sudden stop andthe excessive scraping up of the lubricant by the head during seekingshould be avoided. Thus, the weakly adsorbed layer, which is easilymobile on the disk surface, has an adverse effect on stiction contraryto durability. For this reason, the weakly adsorbed layer should be aslittle as possible. If a conventional lubricant of the adsorption typeis applied to the entire surface of the disk and the data region aloneis washed to remove the weakly adsorbed layer, it necessarily followsthat the lubricating film in the data region decreases in thickness. Atthe present time, there is by far a smaller chance of contact sliding inthe data region than in the CSS region; however, in the future magneticdisk apparatus in which the flying height of the head will decreasefurther, there will be a stronger chance of contact sliding between thehead and disk even in the data region. Thus, there will be, in a nearfuture, a demand for the data region to have good durability. Thisimplies that the lubricating film in the data region should be thickenough to endure occasional contact sliding.

These technical problems are not solved completely by theabove-mentioned prior art technologies. The technology disclosed inJapanese Patent Laid-open No. 111292/1994 provides the respectiveregions with the desired lubricating characteristics by coating the CSSregion with a liquid lubricant and the data region with a solidlubricant. This technology suffers the disadvantage of requiring acomplex process to form the lubricant films. The technology disclosed inJapanese Patent Laid-open No. 53027/1992 ensures low stiction in thedata region and good durability in the CSS region by forming thelubricating films such that the lubricating film in the data region isthinner than the lubricating film in the CSS region. This technology,however, is not satisfactory because it is necessary to maintain acertain thickness for the lubricating film in the data region in orderto ensure good durability. At the present time, there is no effectivemeans to ensure satisfactory slide reliability for a disk having a CSSregion and data region formed thereon.

The present invention was completed to address the above-mentionedproblems involved in the prior art technology. It is an object of thepresent invention to provide an effective means to ensure satisfactoryslide reliability for a disk having a CSS region and data region formedthereon. It is another object of the present invention to provide ahigh-performance magnetic disk and magnetic recording/reproducing devicethat employ such means.

SUMMARY OF THE INVENTION

The magnetic disk according to the present invention is characterized bythe provision of lubricating layers formed thereon in a unique manner asmentioned below. In the data region in the magnetic disk, the weaklyadsorbed lubricating layer is as small as possible to so as to ensurelow stiction, but the lubricating film is thick enough to endure contactsliding (between the magnetic head and the magnetic disk) that mightoccasionally occur. This object is achieved by using a lubricant thatstrongly adsorbs to the surface of the magnetic disk or by treating theapplied lubricant afterward. In the CSS region in the magnetic disk, aweakly adsorbed lubricating layer less liable to stiction is formed, soas to ensure satisfactory durability and take into consideration thefact that the lubricant easily moves to the head slider. The presentinvention discloses the magnetic disk, the process for productionthereof, and the magnetic recording/reproducing device mentioned below.

The first aspect of the present invention resides in a magnetic diskhaving a seed layer, a magnetic layer, and a protective layersequentially laminated on a non-magnetic substrate, characterized inthat the disk has a CSS region and a data region, the CSS region havinga protective layer with a surface roughness greater than or equal to Ra10 nm at the place where the magnetic head slider is positioned when themagnetic disk starts and stops rotating, the data region having aprotective layer with a surface roughness smaller than or equal to Ra 3rm at the place where the magnetic head slider is positioned while themagnetic disk is rotating, the protective layer being coated with alubricating film which contains at least one member selected fromperfluoropolyether compounds expressed by the formulas (I) to (III)below,

R₁—X—(CF₂CF₂O)_(m)—(CF₂O)_(n)—X—R₂  (I)

F(CF₂CF₂CF₂—O)_(n)—C₂F₄—X—R₃  (II)

F—(CF(CF₃)—CF₂—O)_(n)—CF(CF₃)—X—R₄  (III)

(where m and n are integers; R₁, R₂, R₃, and R₄ are hydrocarbon chains;and X is a divalent binding group) the lubricating film is composed of alubricant which is firmly fixed to the surface of said protective filmand another lubricant which is weakly fixed to the surface of saidprotective film, the lubricating film formed in the CSS regioncontaining a lubricant which is weakly fixed in an amount not less than10% of the total amount of the lubricant in the CSS region, thelubricating film formed in the data region containing a lubricant whichis weakly fixed in an amount less than 10% of the total amount of thelubricant in the data region.

The second aspect of the present invention resides in a magnetic disk asdefined in the first aspect, the magnetic disk being characterized inthat the lubricating film is composed of a lubricant which is firmlyfixed to the surface of the protective layer such that it is not washedout by a perfluorocarbon solvent, and another lubricant which is weaklyfixed to the surface of the protective layer such that it is washed outby a perfluorocarbon solvent.

The third aspect of the present invention resides in a magnetic diskhaving a seed layer, a magnetic layer, and a protective layersequentially laminated on a non-magnetic substrate, characterized inthat the disk has a CSS region and a data region, the CSS region havinga protective layer with a surface roughness greater than or equal to Ra10 nm at the place where the magnetic head slider is positioned when themagnetic disk starts and stops rotating, the data region having aprotective layer with a surface roughness smaller than or equal to Ra 3nm at the place where the magnetic head slider is positioned while themagnetic disk is rotating, the protective layer being coated with alubricant which contains at least one member selected fromperfluoropolyether compounds expressed by the formulas (I) to (III)above, the lubricant being applied to the entire surface of the magneticdisk, the entire surface of the magnetic disk being heated above 80° C.or the entire surface or the data region being irradiated withultraviolet rays, the CSS region being subsequently washed with a perfluorocarbon solvent, such that the lubricating film formed in the CSSregion has a thickness greater than equal to 1.5 nm and the lubricatingfilm formed in the data region has a thickness greater than or equal to1 nm.

The fourth aspect of the present invention resides in a magnetic diskhaving a seed layer, a magnetic layer, and a protective layersequentially laminated on a non-magnetic substrate, characterized inthat the disk has a CSS region and a data region, the CSS region havinga protective layer with a surface roughness greater than or equal to Ra10 nm at the place where the magnetic head slider is positioned when themagnetic disk starts and stops rotating, the data region having aprotective layer with a surface roughness smaller than or equal to Ra 3nm at the place where the magnetic head slider is positioned while saidmagnetic disk is rotating, the protective layer being coated with alubricant which contains at least one member selected fromperfluoropolyether compounds expressed by the formulas (I) to (III)above, the lubricant being applied to the entire surface of the magneticdisk, the entire surface of the magnetic disk being heated above 80° C.or the entire surface or the data region being irradiated withultraviolet rays, the entire surface of the magnetic disk being washedwith a perfluorocarbon solvent, subsequently the CSS region being coatedwith a perfluorocarbon compound having adsorptive functional groupsselected from perfluoropolyether compounds expressed by the formulas (I)to (III) above, such that the lubricating film formed in the CSS regionhas a thickness greater than or equal to 1.5 nm and the lubricating filmformed in the data region has a thickness greater than or equal to 1 nm.

The fifth aspect of the present invention resides in a magnetic diskhaving a seed layer, a magnetic layer, and a protective layersequentially laminated on a non-magnetic substrate, characterized inthat the disk has a CSS region and a data region, the CSS region havinga protective layer with a surface roughness greater than or equal to Ra10 nm at the place where the magnetic head slider is positioned when themagnetic disk starts and stops rotating, the data region having aprotective layer with a surface roughness smaller than or equal to Ra 3nm at the place where the magnetic head slider is positioned while saidmagnetic disk is rotating, the protective layer being coated with alubricant which contains at least one member selected fromperfluoropolyether compounds expressed by the formulas (I) to (III)above, the lubricant being applied to the entire surface of the magneticdisk, the entire surface of the magnetic disk being heated above 80° C.or the entire surface or the data region being irradiated withultraviolet rays, the entire surface of the magnetic disk being washedwith a perfluorocarbon solvent, subsequently the data region beingcoated with a perfluorocarbon compound having functional groupschemically reactive with the surface of said protective film selectedfrom perfluoropolyether compounds expressed by the formulas (I) to (III)above, such that the lubricating film formed in the CSS region has athickness greater than or equal to 1.5 nm and the lubricating filmformed in the data region has a thickness greater than or equal to 1 nm.

The sixth aspect of the present invention resides in a magnetic diskhaving a seed layer, a magnetic layer, and a protective layersequentially laminated on a non-magnetic substrate, characterized inthat the disk has a CSS region and a data region, the CSS region havinga protective layer with a surface roughness greater than or equal to Ra10 nm at the place where the magnetic head slider is positioned when themagnetic disk starts and stops rotating, the data region having aprotective layer with a surface roughness smaller than or equal to Ra 3nm at the place where the magnetic head slider is positioned while themagnetic disk is rotating, the protective layer being coated with alubricant which contains at least one member selected fromperfluoropolyether compounds having functional groups chemicallyreactive with the surface of said protective film expressed by theformulas (I) to (III) above, the lubricant being applied to the entiresurface of the magnetic disk, the entire surface of the magnetic diskbeing heated above 80° C. or the entire surface or the data region beingirradiated with ultraviolet rays, the entire surface of the magneticdisk being washed with a perfluorocarbon solvent, subsequently the dataregion being coated with a perfluorocarbon compound having functionalgroups chemically reactive with the surface of said protective filmselected from perfluoropolyether compounds expressed by the formulas (I)to (III) above, such that the lubricating film formed in the CSS regionhas a thickness greater than or equal to 1.5 nm and the lubricating filmformed in the data region has a thickness greater than or equal to 1 nm.

The seventh aspect of the present invention resides in a process forproducing a magnetic disk having a seed layer, a magnetic layer, aprotective layer, and a lubricating layer sequentially laminated on anon-magnetic substrate, the process comprising forming the CSS regionhaving a protective layer with a surface roughness greater than or equalto Ra 10 nm at the place where the magnetic head slider is positionedwhen the magnetic disk starts and stops rotating, forming the dataregion having a protective layer with a surface roughness smaller thanequal to Ra 3 nm at the place where the magnetic head slider ispositioned while the magnetic disk is rotating, coating the surface ofsaid protective layer all over the magnetic disk with a lubricant whichcontains at least one member selected from perfluoropolyether compoundsexpressed by the formulas (I) to (III) above, heating the entire surfaceof the magnetic disk above 80° C. or irradiating the entire surface ofthe magnetic disk or the data region with ultraviolet rays, and washingthe CSS region with a perfluorocarbon solvent, such that the lubricatingfilm formed in the CSS region has a thickness greater than or equal to1.5 nm and the lubricating film formed in the data region has athickness greater than or equal to 1 nm.

The eighth aspect of the present invention resides in a process forproducing a magnetic disk as defined in the seventh aspect, whichfurther comprises, after washing the entire surface of the magnetic diskwith a perfluorocarbon solvent, coating the CSS region with aperfluoropolyether compound having adsorptive functional groups selectedfrom the perfluoropolyether compounds expressed by the formulas (I) to(III) above, such that the lubricating film formed in the CSS region hasa thickness greater than or equal to 1.5 nm and the lubricating filmformed in the data region has a thickness greater than or equal to 1 nm.

The ninth aspect of the present invention resides in a process forproducing a magnetic disk as defined in the seventh aspect, whichfurther comprises, after washing the entire surface of the magnetic diskwith a perfluorocarbon solvent, applying a perfluoropolyether compoundhaving functional groups chemically reactive with the surface of theprotective film which is selected from the perfluoropolyether compoundsexpressed by the formulas (I) to (III) above, such that the lubricatingfilm formed in the CSS region has a thickness greater than or equal to1.5 nm and the lubricating film formed in the data region has athickness greater than or equal to 1 nm.

The tenth aspect of the present invention resides in a process forproducing a magnetic disk as defined in the seventh aspect, whichfurther comprises, after heating the entire surface of the magnetic diskabove 80° C. or irradiating it with ultraviolet rays, applying to theentire surface of the magnetic disk a perfluoropolyether compound-havingadsorptive functional groups which is selected from theperfluoropolyether compounds expressed by the formulas (I) to (III)above, and, after washing the data region with a perfluorocarbonsolvent, applying a perfluoropolyether compound having chemicallyreactive functional groups which is selected from perfluoropolyethercompounds expressed by the formulas (I) to (III) above, such that thelubricating film formed in the CSS region has a thickness greater thanor equal to 1.5 nm and the lubricating film formed in the data regionhas a thickness greater than or equal to 1 nm.

The eleventh aspect of the present invention resides in a magneticrecording/reproducing device composed of a magnetic head, a magnetichead slider carrying the magnetic head, and a magnetic disk having aseed layer, a magnetic layer, and a protective layer sequentiallylaminated on a non-magnetic substrate, characterized in that the diskhas a CSS region and a data region, the CSS region having a protectivelayer with a surface roughness greater than or equal to Ra 10 rim at theplace where the magnetic head slider is positioned when the magneticdisk starts and stops rotating, the data region having a protectivelayer with a surface roughness smaller than or equal to Ra 3 nm at theplace where the magnetic head slider is positioned while the magneticdisk is rotating, the protective layer being coated with a lubricatingfilm which contains at least one member selected from perfluoropolyethercompounds expressed by the formulas (I) to (III) above, the lubricatingfilm is composed of a lubricant which is firmly fixed to the surface ofsaid protective film and another lubricant which is weakly fixed to thesurface of said protective film, the lubricating film formed in the CSSregion containing a lubricant which is weakly fixed in an amount notless than 10% of the total amount of the lubricant in the CSS region,the lubricating film formed in the data region containing a lubricantwhich is weakly fixed in an amount less than 10% of the total amount ofthe lubricant in the data region, such that the limiting staticfriction, and dynamic friction that occur in the data region between themagnetic head slider and the magnetic disk are smaller than or equal to1.5 and 1.0, respectively, and the limiting static friction and dynamicfriction that occur in the CSS region between the magnetic head sliderand the magnetic disk are smaller than or equal to 1.0 and 0.5,respectively.

The twelfth aspect of the present invention resides in a magneticrecording/reproducing device composed of a magnetic head, a magnetichead slider carrying the magnetic head, and a magnetic disk having aseed layer, a magnetic layer, and a protective layer sequentiallylaminated on a non-magnetic substrate, characterized in that the diskhas a CSS region and a data region, the CSS region having a protectivelayer with a surface roughness greater than or equal to Ra 10 nm at theplace where the magnetic head slider is positioned when the magneticdisk starts and stops rotating, the data region having a protectivelayer with a surface roughness smaller than or equal to Ra 3 nm at theplace where the magnetic head slider is positioned while the magneticdisk is rotating, the protective layer being coated with a lubricatingfilm which contains at least one member selected from perfluoropolyethercompounds expressed by the formulas (I) to (III) above, the lubricantbeing applied to the entire surface of the magnetic disk, the entiresurface of the, magnetic disk being heated above 80° C. or the entiresurface or the data region being irradiated with ultraviolet rays, theCSS region being subsequently washed with a perfluorocarbon solvent,such that the lubricating film formed in the CSS region has a thicknessgreater than or equal to 1.5 nm and the lubricating film formed in thedata region has a thickness greater than or equal to 1 nm, and thelimiting static friction and dynamic friction that occur in the dataregion between the magnetic head slider and the magnetic disk aresmaller than or equal to 1.5 and 1.0, respectively, and the limitingstatic friction and dynamic friction that occur in the CSS regionbetween the magnetic head slider and the magnetic disk are smaller thanor equal to 1.0 and 0.5, respectively.

The thirteenth aspect of the present invention resides in a magneticrecording/reproducing device as the twelfth aspect, which ischaracterized in that the magnetic disk has the data region which iscoated, after washing with a fluorocarbon solvent, with aperfluoropolyether compound having adsorptive functional groups which isselected from the perfluoropolyether compounds expressed by the formulas(I) to (III) above, such that the lubricating film formed in the CSSregion has a thickness greater than or equal to 1.5 nm and thelubricating film formed in the data region has a thickness greater thanor equal to 1 nm.

The fourteenth aspect of the present invention resides in a magneticrecording/reproducing device as defined in the twelfth aspect, which ischaracterized in that the entire surface of the magnetic disk is coated,after the washing of the data region with a fluorocarbon solvent, with aperfluoropolyether compound having functional groups chemically reactivewith the protective film which is selected from the perfluoropolyethercompounds expressed by the formulas (I) to (III) above, such that thelubricating film formed in the CSS region has a thickness greater thanor equal to 1.5 nm and the lubricating film formed in the data regionhas a thickness greater than or equal to 1 nm.

The fifteenth aspect of the present invention resides in a magneticrecording/reproducing device composed of a magnetic head, a magnetichead slider carrying the magnetic head, and a magnetic disk having aseed layer, a magnetic layer, and a protective layer sequentiallylaminated on a non-magnetic substrate, characterized in that the diskhas a CSS region and a data region, the CSS region having a protectivelayer with a surface roughness greater than or equal to Ra 10 nm at theplace where the magnetic head slider is positioned when the magneticdisk starts and stops rotating, the data region having a protectivelayer with a surface roughness smaller than or equal to Ra 3 nm at theplace where the magnetic head slider is positioned while the magneticdisk is rotating, after coating the surface of the protective film allover the magnetic disk with at least one perfluoropolyether compoundexpressed by the formulas (I) to (III) above, heating the entire surfaceof the magnetic disk above 80° C. or irradiating the entire surface ofthe magnetic disk or the data region with ultraviolet rays, coating theentire surface of the magnetic disk with a perfluoropolyether compoundhaving adsorptive functional groups which is selected from theperfluoropolyether compounds expressed by the formulas (I) to (III)above, and, after washing the data region with a perfluorocarbonsolvent, applying a perfluoropolyether compound having chemicallyreactive functional groups which is selected from the perfluoropolyethercompounds expressed by the formulas (I) to (III) above, such that thelubricating film formed in the CSS region has a thickness greater thanor equal to 1.5 nm and the lubricating film formed in the data regionhas a thickness greater than 1 nm, and the limiting static friction anddynamic friction that occur in the data region between the magnetic headslider and the magnetic disk are smaller than or equal to 1.5 and 1.0,respectively, and the limiting static friction and dynamic friction thatoccur in the CSS region between the magnetic head slider and themagnetic disk are smaller than or equal to 1.0 and 0.5, respectively.

The sixteenth aspect of the present invention resides in a magnetic diskhaving a seed layer, a magnetic layer, and a protective layersequentially laminated on a non-magnetic substrate, characterized inthat the disk has a CSS region and a data region, the CSS region havinga protective layer with a surface roughness greater than or equal to Ra10 nm at the place where the magnetic head slider is positioned when themagnetic disk starts and stops rotating, the data region having aprotective layer with a surface roughness smaller than or equal to Ra 3nm at the place where the magnetic head slider is positioned while themagnetic disk is rotating, the protective layer being coated with alubricant which contains at least one member selected fromperfluoropolyether compounds expressed by the formulas (IV) to (XIII)below,

F(CF₂CF₂CF₂O)_(n)—C₂F₄—CONH—C₃H₆—Si(OC₂H₅)₃  (IV)

F(CF(CF₃)—CF₂O)_(n)—CF(CF₃)—CONH—C₃H₆—Si(OC₂H₅)₃  (V)

(C₂H₅O)₃Si—C₃H₆—NHCO—(CF₂CF₂O)_(m)—(CF₂O)_(n)—CONH—C₃H₆—Si(OC₂H₅)₃  (VI)

C₆H₅—O—C₆H₄—H₃N+—OCO—(CF₂CF₂O)_(m)—(CF₂O)_(n)—COO—+NH₃—C₆H₄—O—C₆H₅  (VII)

F(CF₂CF₂CF₂—O)_(n)—C₂F₄—CH₂OH  (VIII)

HO—CH₂—(CF₂CF₂O)_(m)—(CF₂O)_(n)—CH₂OH  (IX)

HO—(CH₂CH₂—O)_(p)—CH₂CF₂—(CF₂CF₂O)_(m)—(CF₂O)_(n)—OCF₂CH₂(O—CH₂CH₂)_(q)—OH  (X)

F(CF₂CF₂CF₂O)_(n)—C₂F₄—COO—+NH₃—C₆H₄—O—C₆H₅  (XI)

F(CF(CF₃)—CF₂O)_(n)—CF(CF₃)—COO—+NH₃—C₆H₄—O—C₆H₅  (XII)

(where m, n, p, and q are integers) all over the surface of the magneticdisk, the entire surface of the magnetic disk being heated above 80° C.or the data region being irradiated with ultraviolet rays, the CSSregion being subsequently washed with a perfluorocarbon solvent, suchthat the lubricating film formed in the CSS region has a thicknessgreater than or equal to 1.5 nm and the lubricating film formed in thedata region has a thickness greater than or equal to 1 nm.

The seventeenth aspect of the present invention resides in a magneticdisk having a seed layer, a magnetic layer, and a protective layersequentially laminated on a non-magnetic substrate, characterized inthat the disk has a CSS region and a data region, the CSS region havinga protective layer with a surface roughness greater than or equal to Ra10 nm at the place where the magnetic head slider is positioned when themagnetic disk starts and stops rotating, the data region having aprotective layer with a surface roughness smaller than or equal to Ra 3nm at the place where the magnetic head slider is positioned while themagnetic disk is rotating, the protective layer being coated with alubricant which contains at least one member selected fromperfluoropolyether compounds expressed by the formulas (IV) to (XIII)above, all over the surface of the magnetic disk, the entire surface ofthe magnetic disk being heated above 80° C. or the data region beingirradiated with ultraviolet rays, the entire surface of the magneticdisk being washed with a perfluorocarbon solvent and the CSS regionbeing coated with a perfluoropolyether compound having adsorptivefunctional groups which is selected from the perfluoropolyethercompounds expressed by the formulas (VII) to (XIII) above, such that thelubricating film formed in the CSS region has a thickness greater thanor equal to 1.5 nm and the lubricating film formed in the data regionhas a thickness greater than 1 nm.

The eighteenth aspect of the present invention resides in a magneticdisk having a seed layer, a magnetic layer, and a protective layersequentially laminated on a non-magnetic substrate, characterized inthat the disk has a CSS region and a data region, the CSS region havinga protective layer with a surface roughness greater than or equal to Ra10 nm at the place where the magnetic head slider is positioned when themagnetic disk starts and stops rotating, the data region having aprotective layer with a surface roughness smaller than or equal to Ra 3nm at the place where the magnetic head slider is positioned while themagnetic disk is rotating, the protective layer being coated with alubricant which contains at least one member selected fromperfluoropolyether compounds expressed by the formulas (IV) to (XIII)above, the lubricant being applied to the entire surface of the magneticdisk, the entire surface of the magnetic disk being heated above 80° C.or the entire surface of the magnetic disk or the data region beingirradiated with ultraviolet rays, the data region being subsequentlywashed with a perfluorocarbon solvent, and coating the data region witha perfluoropolyether compound having functional groups reactive with thesurface of the protective film which is selected from theperfluoropolyether compounds expressed by the formulas (IV) to (VI)above, such that the lubricating film formed in the CSS region has athickness greater than or equal to 1.5 nm and the lubricating filmformed in the data region has a thickness greater than or equal to 1 nm.

The nineteenth aspect of the present invention resides in a magneticdisk having a seed layer, a magnetic layer,-and a protective layersequentially laminated on a non-magnetic substrate, characterized inthat the disk has a CSS region and a data region, the CSS region havinga protective layer with a surface roughness greater than equal to Ra 10nm at the place where the magnetic head slider is positioned when themagnetic disk starts and stops rotating, the data region having aprotective layer with a surface roughness smaller than or equal to Ra 3nm at the place where the magnetic head slider is positioned while saidmagnetic disk is rotating, the protective layer being coated with alubricant which contains at least one member selected fromperfluoropolyether compounds expressed by the formulas (IV) to (VI)above, the lubricant being applied to the entire surface of the magneticdisk, the entire surface of the magnetic disk being heated above 80° C.or the entire surface of the magnetic disk or the data region beingirradiated with ultraviolet rays, the surface of said protective filmbeing coated all over the magnetic disk with a perfluoropolyethercompound having adsorptive functional groups which is selected from theperfluoropolyether compounds expressed by the formulas (VII) to (XIII)above, the data region being subsequently washed with a perfluorocarbonsolvent, and coating the data region with a perfluoropolyether compoundhaving functional groups chemically reactive with the surface of theprotective film which is selected from the perfluoropolyether compoundsexpressed by the formulas (IV) to (VI) above, such that the lubricatingfilm formed in the CSS region has a thickness greater than equal to 1.5nm and the lubricating film formed in the data region has a thicknessgreater than or equal to 1 nm.

The twentieth aspect of the present invention resides in a magnetic diskhaving a seed layer, a magnetic layer, a protective layer, and alubricating layer sequentially laminated on a non-magnetic substrate,characterized in that the disk has a CSS region and a data region, theCSS region having a protective layer with a surface roughness greaterthan or equal to Ra 10 nm at the place where the magnetic head slider ispositioned when the magnetic disk starts and stops rotating, the dataregion having a protective layer with a surface roughness smaller thanor equal to Ra 3 nm at the place where the magnetic head slider ispositioned while the magnetic disk is rotating, the protective layerbeing coated with a lubricant which contains at least one memberselected from perfluoropolyether compounds expressed by the formulas(IV) to (XIII) above, the lubricant being applied to the entire surfaceof the magnetic disk, the entire surface of the magnetic disk beingheated above 80° C. or the entire surface of the magnetic disk or thedata region being irradiated with ultraviolet rays, the CSS region beingsubsequently washed with a perfluorocarbon solvent, such that thelubricating film formed in the CSS region has thickness greater than orequal to 1.5 nm and the lubricating film formed in the data region has athickness greater than or equal to 1 nm.

The twenty-first aspect of the present invention resides in a processfor producing a magnetic disk having a seed layer, a magnetic layer, aprotective layer, and a lubricating layer sequentially laminated on anon-magnetic substrate, said process comprising forming a CSS regionhaving a protective layer with a surface roughness greater than or equalto Ra 10 nm at the place where the magnetic head slider is positionedwhen the magnetic disk starts and stops rotating, forming a data regionhaving a protective layer with a surface roughness smaller than or equalto Ra 3 nm at the place where the magnetic head slider is positionedwhile the magnetic disk is rotating, coating the surface of theprotective layer all over the magnetic disk with a lubricant whichcontains at least one member selected from perfluoropolyether compoundsexpressed by the formulas (IV) to (XIII) above, heating the entire surface of the magnetic disk above 80° C. or irradiating the entire surfaceof the magnetic disk or the data region with ultraviolet rays, andwashing the entire surface of the magnetic disk with a perfluorocarbonsolvent, and coating the CSS region with a perfluoropolyether compoundhaving adsorptive functional groups which is selected from theperfluoropolyether compounds expressed by the formulas (VII) to (XIII)above, such that the lubricating film formed in the CSS region has athickness greater than or equal to 1.5 nm and the lubricating filmformed in the data region has a thickness greater than or equal to 1 nm.

The twenty-second aspect of the present invention resides in a processfor producing a magnetic disk having a seed layer, a magnetic layer, aprotective layer, and a lubricating layer sequentially laminated on anon-magnetic substrate, said process comprising forming a CSS regionhaving a protective layer with a surface roughness greater than or equalto Ra 10 nm at the place where the magnetic head slider is positionedwhen the magnetic disk starts and stops rotating, forming a data regionhaving a protective layer with a surface roughness smaller than or equalto Ra 3 nm at the place where the magnetic head slider is positionedwhile the magnetic disk is rotating, coating the surface of theprotective layer all over the magnetic disk with a lubricant whichcontains at least one member selected from perfluoropolyether compoundsexpressed by the formulas (IV) to (XIII) above, heating the entiresurface of the magnetic disk above 80° C. or irradiating the entiresurface of the magnetic disk or the data region with ultraviolet rays,and washing the entire surface of the magnetic disk with aperfluorocarbon solvent, and coating the data region with aperfluoropolyether compound having functional groups chemically reactivewith the surface of the protective layer which is selected from theperfluoropolyether compounds expressed by the formulas (IV) to (VI)above, such that the lubricating film formed in the CSS region has athickness greater than or equal to 1.5 nm and the lubricating filmformed in the data region has a thickness greater than or equal to 1 nm.

The twenty-third aspect of the present invention resides in a processfor producing a magnetic disk having a seed layer, a magnetic layer, aprotective layer, and a lubricating layer sequentially laminated on anon-magnetic substrate, said process comprising forming a CSS regionhaving a protective layer with a surface roughness greater than or equalto Ra 10 nm at the place where the magnetic head slider is positionedwhen the magnetic disk starts and stops rotating, forming a data regionhaving a protective layer with a surface roughness smaller than or equalto Ra 3 nm at the place where the magnetic head slider is positionedwhile the magnetic disk is rotating, coating the surface of theprotective layer all over the magnetic disk with a lubricant whichcontains at least one member selected from perfluoropolyether compoundshaving functional groups chemically reactive with the surface of theprotective film expressed by the formulas (IV) to (VI) above, heatingthe entire surface of the magnetic disk above 80° C. or irradiating theentire surface of the magnetic disk with ultraviolet rays, coating theentire surface of the magnetic disk wit h a perfluoropolyether compoundhaving adsorptive functional groups which is selected fromperfluoropolyether compounds expressed by the formulas (VII) to (XIII),and washing the data region with a perfluorocarbon solvent, and coatingwith a perfluoropolyether compound having functional groups chemicallyreactive with the surface of the protective layer which is selected fromthe perfluoropolyether compounds expressed by the formulas (IV) to (VI)above, such that the lubricating film formed in the CSS region has athickness greater than or equal to 1.5 nm and the lubricating filmformed in the data region has a thickness greater than or equal to 1 nm.

The twenty-fourth aspect of the present invention resides in a magneticrecording/reproducing device comprising a magnetic head, a magnetic headslider carrying the magnetic head, and a magnetic disk having a seedlayer, a magnetic layer, and a protective layer sequentially laminatedon a non-magnetic substrate, characterized in that the disk has a CSSregion and a data region, the CSS region having a protective layer witha surface roughness greater than or equal to Ra 10 nm at the place wherethe magnetic head slider is positioned when the magnetic disk starts andstops rotating, the data region having a protective layer with a surfaceroughness smaller than or equal to Ra 3 nm at the place where themagnetic head slider is positioned while the magnetic disk is rotating,the protective layer being coated with a lubricating film which containsat least one member selected from perfluoropolyether compounds expressedby the formulas (IV) to (XIII) above, subsequently the entire surface ofthe magnetic disk is heated above 80° C. or the entire surface of themagnetic disk or the data region is irradiated with ultraviolet rays,and the data region is washed with a perfluorocarbon solvent, such thatthe lubricating film formed in the CSS region has a thickness greaterthan or equal to 1.5 nm and the lubricating film formed in the dataregion has a thickness greater than or equal to 1 nm, and the limitingstatic friction and dynamic friction that occur in the data regionbetween the magnetic head slider and the magnetic disk are smaller thanor equal to 1.5 and 1.0, respectively, and the limiting static frictionand dynamic friction that occur in the CSS region between the magnetichead slider and the magnetic disk are smaller than or equal to 1.0 and0.5, respectively.

The twenty-fifth aspect of the present invention resides in a magneticrecording/reproducing device composed of a magnetic head, a magnetichead slider carrying the magnetic head, and a magnetic disk having aseed layer, a magnetic layer, and a protective layer sequentiallylaminated on a non-magnetic substrate, characterized in that the diskhas a CSS region and a data region, the CSS region having a protectivelayer with a surface roughness greater than or equal to Ra 10 nm at theplace where the magnetic head slider is positioned when the magneticdisk starts and stops rotating, the data region having a protectivelayer with a surface roughness smaller than or equal to Ra 3 nm at theplace where the magnetic head slider is positioned while the magneticdisk is rotating, the protective layer being coated with a lubricatingfilm which contains at least one member selected from perfluoropolyethercompounds expressed by the formulas (IV) to (XIII) above, subsequentlythe entire surface of the magnetic disk is heated above 80° C. or theentire surface of the magnetic disk or the data region is irradiatedwith ultraviolet rays, and the entire surface of the magnetic disk iswashed with a perfluorocarbon solvent, the CSS region is coated with aperfluoropolyether compound having adsorptive functional groups which isselected from the perfluoropolyether compounds expressed by the formulas(VII) to (XIII) above, such that the lubricating film formed in the CSSregion has a thickness greater than or equal to 1.5 nm and thelubricating film formed in the data region has a thickness greater thanor equal to 1 nm, and the limiting static friction and dynamic frictionthat occur in the data region between the magnetic head slider and themagnetic disk are smaller than or equal to 1.5 and 1.0, respectively,and the limiting static friction and dynamic friction that occur in theCSS region between the magnetic head slider and the magnetic disk aresmaller than or equal to 1.0 and 0.5, respectively.

The twenty-sixth aspect of the present invention resides in a magneticrecording/reproducing device composed of a magnetic head, a magnetichead slider carrying the magnetic-head, and a magnetic disk having aseed layer, a magnetic layer, and a protective layer sequentiallylaminated on a non-magnetic substrate, characterized in that the diskhas a CSS region and a data region, the CSS region having a protectivelayer with a surface roughness greater than or equal to Ra 10 nm at theplace where the magnetic head slider is positioned when the magneticdisk starts and stops rotating, the data region having a protectivelayer with a surface roughness smaller than or equal to Ra 3 nm at theplace where the magnetic head slider is positioned while the magneticdisk rotating, the protective layer being coated all over the magneticdisk with at least one member selected from perfluoropolyether compoundsexpressed by the formulas (IV) to (XIII) above, subsequently the entiresurface of the magnetic disk being heated above 80° C. or the entiresurface of the magnetic disk or the data region being irradiated withultraviolet rays, and the data region being washed with aperfluorocarbon solvent, the data region being coated with aperfluoropolyether compound having functional groups chemically reactivewith the surface of the protective film which is selected from theperfluoropolyether compounds expressed by the formulas (IV) to (VI)above, such that the lubricating film formed in the CSS region has athickness greater than 1.5 nm and the lubricating film formed in thedata region has a thickness greater than 1 nm, and the limiting staticfriction and dynamic friction that occur in the data region between themagnetic head slider and the magnetic disk are smaller than or equal to1.5 and 1.0, respectively, and the limiting static friction and dynamicfriction that occur in the CSS region between the magnetic head sliderand the magnetic disk are smaller than or equal to 1.0 and 0.5,respectively.

The twenty-seventh aspect of the present invention resides in a magneticrecording/reproducing device composed of a magnetic head, a magnetichead slider carrying the magnetic head, and a magnetic disk having aseed layer, a magnetic layer, a protective layer, and a lubricatinglayer sequentially laminated on a non-magnetic substrate, characterizedin that the disk has a CSS region and a data region, the CSS regionhaving a protective layer with a surface roughness greater than or equalto Ra 10 nm at the place where the magnetic head slider is positionedwhen the magnetic disk starts and stops rotating, the data region havinga protective layer with a surface roughness smaller than or equal to Ra3 nm at the place where the magnetic head slider is positioned while themagnetic disk is rotating, the protective layer being coated all overthe magnetic disk with at least one member selected fromperfluoropolyether compounds having functional groups chemicallyreactive with the protective layer, expressed by the formulas (IV) to(VI) above, subsequently the entire surface of the magnetic disk beingheated above 80° C. or irradiated with ultraviolet rays, the entiresurface of the magnetic disk being coated with a perfluoropolyethercompound having adsorptive functional groups selected from theperfluoropolyether expressed by the formulas (VII) to (XIII) above, andthe data region being washed with a perfluorocarbon solvent, the dataregion being coated with a perfluoropolyether compound having functionalgroups chemically reactive with the surface of the protective film whichis selected from the perfluoropolyether compounds expressed by theformulas (IV) to (VI) above, such that the lubricating film formed inthe CSS region has a thickness greater than or equal to 1.5 nm and thelubricating film formed in the data region has a thickness greater thanor equal to 1 nm, and the limiting static friction and dynamic frictionthat occur in the data region between the magnetic head slider and themagnetic disk are smaller than or equal to 1.5 and 1.0, respectively,and the limiting static friction and dynamic friction that occur in theCSS region between the magnetic head slider and the magnetic disk aresmaller than or equal to 1.0 and 0.5, respectively.

The twenty-eighth aspect of the present invention resides in themagnetic disk as defined in the first aspect which has a diametersmaller than or equal to 88.9 mm.

The twenty-ninth aspect of the present invention resides in the magneticdisk as defined in the seventh aspect which has a diameter smaller thanor equal to 88.9 mm.

The thirtieth aspect of the present invention resides in the magneticdisk as defined in the eleventh aspect which has a diameter smaller thanor equal to 88.9 mm.

According to the present invention, the CSS region has a lubricatinglayer which is composed of a firmly fixed lubricant and a weakly fixedlubricant so as to ensure good durability, and the data region has alubricating layer composed mainly of a firmly fixed lubricant so as toreduce stiction. The lubricating layer (of weakly fixed lubricant) inthe data region needs to have a certain thickness so that it endurescontact sliding that might accidentally occur in the data region as aresult of reduction in the flying height of the head. To this end, it isnecessary not only to select a lubricant having reactive or adsorptivefunctional groups or to increase the thickness of the layer of thefirmly fixed lubricant by heating or UV treatment, but also to coat thedata region twice. Conversely, the CSS region is coated with thelubricant twice if the weakly fixed lubricant is small in amount. Thelubricating layer constructed in this manner permits the data region andthe CSS region to exhibit satisfactory sliding performance required of areliable magnetic disk and magnetic disk apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is a perspective view showing the magnetic disk prepared inExample 1 of the present invention and

FIG. 1(b) is a sectional view showing the boundary between the CSSregion and the data zone.

FIG. 2(a) is a sectional view and

FIG. 2(b) is a top view of the apparatus used for a CSS test andstiction test.

FIG. 3 is a sectional view of the magnetic recording/reproducing devicepertaining to the embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention will be described in more detail with reference to thefollowing examples, which are not intended to restrict the scope of theinvention.

Example 1

A substrate of aluminum alloy (3.5 inches in diameter) with its surfacemirror-finished was coated by sputtering sequentially with an NiP seedlayer (10 μm thick), a Cr layer (0.5 μm thick), a Co—Cr-Pt layer (60 nmthick), and a carbon protective layer (20 nm thick), to produce amagnetic disk. The region (15-20 mm in radius) of this magnetic diskunderwent electrostatic coating with fluorinated resin particles (0.5 μmin diameter). The entire surface of the magnetic disk underwent etching(10 nm deep) with oxygen. The fluorinated resin particles were removedby water washing. In this way there were formed uniformly cylindricalprotuberances (0.5 μm in diameter) in the region covering the radiusfrom 15 to 20 mm. In this region was formed a CSS region having a centerline average roughness of Ra 15 nm, and in another region was formed asmooth data region having a center line average roughness of Ra 1.2 nm.

Next, the magnetic disk was dipped (for coating) in a solution (1)containing in a fluoride-containing solvent (“PF5052” from Sumitomo 3MLimited) 0.01 wt % of perfluoropolyether compound expressed by theformula (IV) below.

F(CF₂CF₂CF₂O)_(n)—C₂F₄—CONH—C₃H₆—Si(OC₂H₅)₃  (IV)

The conditions of dip coating are as follows.

Dip rate in the solution: 10 mm/s

Residence time in the solution: 180 s

Raising rate from the solution: 2.5 mm/s After complete drying, thecoated magnetic disk was heated at 100° C. for 2 hours. This heattreatment causes the perfluoropolyether compound (IV) to chemicallyreact with the surface of the protective layer and hence to firmly fixto the surface of the magnetic disk. Subsequently, the magnetic disk wasdipped (for coating in the same manner as mentioned above) in a solution(2) containing in a fluoride-containing solvent (“PF5052” from Sumitomo3M Limited) 0.001 wt % of perfluoropolyether compound expressed by theformula (XI) below.

F(CF₂CF₂CF₂O)_(n)—C₂F₄—COO—+NH₃—C₆H₄—O—C₆H₅  (XI)

After complete drying, the data region of the coated magnetic disk waswashed with the above-mentioned fluoride-containing solvent. Thiswashing was accomplished by jetting the solvent (50 ml/min) to the dataregion while turning the disk (1000 rpm) by means of a spinner. (Analternative washing method is by turning the disk, with the data regiondipped in the solvent.)

The thus obtained magnetic disk has in the CSS region a lubricatinglayer which has chemically reacted with the surface of the disk. Thislubricating layer is composed of a firmly fixed layer and a weakly fixedlayer of perfluoropolyether compound (XI). In addition, the magneticdisk has in the data region a firmly fixed lubricating layer composedalmost entirely of perfluoropolyether compound (IV). The lubricatinglayers in the data region and CSS region have a thickness of 2.2 nm and2.7 nm, respectively. FIG. 1(a) shows the external appearance of themagnetic disk prepared in this example. FIG. 1(b) is a sectional viewshowing the boundary 3 between the CSS region and the data region.

The sputtered magnetic disk underwent a contact-start-stop (CSS) testand a stiction test under the following conditions using the apparatusshown in FIG. 2(a).

The magnetic disk 7 for measurement is attached (and fixed by the diskpresser 9) to the spindle 8 which is directly connected to the motorplaced at the bottom of the apparatus. The head slider 12 is of thein-line type (20T made of Al₂O₃TiC), with its rail surface coming intocontact in the disk-rotating direction. The head slider 12 is fixed tothe arm 13 which is connected to the load cell 10. The load cell 10 isfixed to the stage 11 which is movable in the radial direction, so thatevaluation for each track is possible. The load cell 10 measures thefrictional force that occurs between the head slider 12 and the magneticdisk 7 during rotation.

For CSS evaluation, start and stop operations of the disk were repeated(up to 100,000 times) at short intervals. After CSS cycles of 1, 50,100, 500, 1000, 5000, 10000, and integral multiples of 10000, the diskwas stopped, the head was allowed to be in contact with the disk for 2seconds, and the disk was turned at 10 rpm. The maximum dynamic frictionat that time was measured. Also, the number of CSS for disk crash tooccur was counted. Disk crash is defined as the state in which thecarbon protective layer (as the undercoat of the lubricating layer) iscompletely worn and the magnetic layer is exposed. Crash gives a visiblewear scar. The experiment was suspended when crash occurred. In the casewhere disk crash occurred within 100,000 cycles, the maximum dynamicfriction force is expressed by the maximum dynamic friction coefficientmeasured up to the CSS cycles before disk crash. The maximum speed ofthe disk is 5400 rpm and the head load is 3.0 g. The disk was run for 20hours, with the head flying (because, the head is usually in the flyingstate in the data region). In anticipation of an accidental disk stop,the disk was stopped at certain intervals (4, 8, 12, 16, and 20 hoursafter the start of experiment). As in the case of measurement in the CSSregion, the head was brought into contact for 2 seconds and then thedisk was run at 10 rpm, and the maximum dynamic friction force wasmeasured. The disk surface was inspected for a wear scar, and theexperiment was suspended as soon as a crash occurred.

Stiction was measured as follows. The head slider was kept in contactwith the disk for 12 hours, the disk was rotated slowly. The limitingstatic friction that occurred immediately after rotation was measured.For measurement, in both the CSS region and data region, the load was3.0 g and the disk speed was 1 rpm. The results of evaluation are shownin Table 1.

TABLE 1 CSS test CSS region Data region Time up Max. Max. to Stictiontest dynamic CSS dynamic occurence Limiting static friction cyclesfriction of wear friction (gf) force up to force scar CSS Data (gf)crash (gf) (h) region region Example 1 1.86 >100000 2.16 >20 1.86 2.12Example 2 1.67 >100000 2.38 >20 1.95 2.36 Example 3 1.49 >1000002.01 >20 1.66 2.43 Comparative 7.86   5000 3.12 >20 1.35 2.31 Example 1Comparative 1.82 >100000 3.51 >20 1.86 27.6 Example 2 comparative1.62 >100000 12.6  8 1.92 2.28 Example 3 Comparative 1.51 >1000002.95 >20 1.69 32.8 Example 4

Comparative Example 1 demonstrates the effect of coating the magneticdisk with the perfluoropolyether compound (IV) alone. Example 1indicated a data region and CSS region which are satisfactory in the CSStest and stiction test, whereas Comparative Example 1 indicated a dataregion which is low in stiction and a CSS region which caused a diskcrash in the CSS test. Comparative Example 2 demonstrates the effect ofnot performing washing on the data region after coating sequentiallywith the perfluoropolyether compound (IV) and the perfluoropolyethercompound (XI). In this case, the CSS region was satisfactory, but thedata region suffered strong stiction.

Example 2

Example 1 was repeated to prepare a magnetic disk by sputtering. Themagnetic disk was dipped in a 0.005 wt % solution of theperfluoropolyether compound (VI) expressed by the formula (VI) below inthe same fluoride-containing solvent as used in Example 1 under the samecondition as in Example 1. Dipping was followed by heat treatment at120° C. for 10 minutes, and the entire surface of the magnetic disk waswashed with the same fluoride-containing disk as mentioned above. Thelubricating layer has a thickness of 0.75 nm.

(C₂H₅O)₃Si—C₃H₆—NHCO—(CF₂CF₂O)_(m)—(CF₂O)_(n)—CONH—C₃H₆—Si(OC₂H₅)₃  (VI)

The fluorine-based lubricant (VIII) expressed by the formula (VIII)below was dissolved in the above-mentioned fluoride-containing solventto give a 0.007 wt % solution.

F(CF₂CF₂CF₂—O)_(n)—C₂F₄—CH₂OH  (VIII)

This solution was applied in the same manner as in Example 1, and thedata region alone was washed with the same fluoride-containing solventas mentioned above. A 0.005 wt % solution of the above-mentionedperfluoropolyether compound (VI) was applied to the data region again byusing the spinner. The thickness of the lubricating layers in the dataregion and CSS region was 1.96 rm and 1.84 nm, respectively.

The lubricating layer formed in this example was tested for CSScharacteristics and stiction characteristics in the same manner as inExample 1. The results are shown in Table 1. This example is superior inboth CSS characteristics and stiction characteristics to ComparativeExample 3 in which the recoating of the perfluoropolyether compound (VI)was not performed. By contrast, Comparative Example 3 gave wear scars inthe data region, although its result in the CSS zone is identical withthat in this example. A probable reason for this that the head flies inthe data zone, but the head comes into contact with the disk (because oflow flying height) while the disk is rotating. The poor-results inComparative Example 3 are due to the fact that the lubricating layer inthe data region is not thick enough to maintain sufficient durability.

Example 3

Example 1 was repeated to prepare a magnetic disk by sputtering. Themagnetic disk was dipped in a 0.005 wt % solution of theperfluoropolyether compound (XIII) expressed by the formula (XIII) belowin the same fluoride-containing solvent as used in Example 1 under thesame condition as in Example 1. Dipping was followed by heat treatmentat 110° C. for 2 hours, and the entire surface of the magnetic disk waswashed with the same fluoride-containing disk as mentioned above. Thelubricating layer has a thickness of 0.8 nm.

The perfluoropolyether compound (VII) expressed by the formula (VII)below was dissolved in the above-mentioned fluoride-containing solventto give a 0.007 wt % solution.

C₆H₅—O—C₆H₄—H₃N+—OCO—(CF₂CF₂O)_(m)—(CF₂O)_(n)—COO—⁺NH₃—C₆H₄—O—C₆H₅  (VII)

This solution was applied in the same manner as in Example 1, and thedata region alone was heated at 1100C for. 2 hours and then washed withthe same fluoride-containing solvent as mentioned above. The thicknessof the layers in the data region and CSS region was 1.85 nm and 2.31 nm,respectively. The lubricating layer formed in this example was testedfor CSS characteristics and stiction characteristics in the same manneras in Example 1. The results are shown in Table 1. This example issuperior in both CSS characteristics and stiction characteristics tocomparative Example 4 in which the washing of the data region was notperformed after the application of the perfluoropolyether compound. Bycontrast, the CSS region in Comparative Example 4 is identical with thatin this example, but strong stiction occurred in the data region.

Example 4

The magnetic disk prepared in Example 1 was mounted on a magneticrecording/reproducing device (for 3.5 inch disk) as schematically shownin FIG. 3. During running, the apparatus was deenergized so as to stopthe head in the data region, and the apparatus was allowed to stand for24 hours. On resumption, the magnetic disk permitted recording andreproducing normally. The same experiment as above was carried out withthe magnetic disk prepared in Comparative Example 5. The apparatus couldnot restart due to strong stiction between the head slider and the diskin the data region.

Comparative Example 1

Example 1 was repeated to produce a magnetic disk by sputtering. Themagnetic disk was dipped in a 0.01 wt % solution of theperfluoropolyether compound (IV) expressed by the formula (IV) below ina fluoride-containing solvent (“PF5052” from Sumitomo 3M Limited) underthe same condition as in Example 1.

F(CF₂CF₂CF₂O)_(n)—C₂F₄—CONH—C₃H₆—Si(OC₂H₅)₃  (IV)

Dipping was followed by complete drying and heat treatment at 110° C.for 2 hours. The thickness of the lubricating layer was 1.3 nm. The diskwas tested for CSS characteristics and stiction characteristics in thesame manner as in Example 1. The results are shown in Table 1.

Comparative Example 2

Example 1 was repeated to produce a magnetic disk by sputtering. Themagnetic disk was dipped in a 0.01 wt % solution of theperfluoropolyether compound (IV) expressed by the formula (IV) below ina fluoride-containing solvent (“PF5052” from Sumitomo 3M Limited) underthe same condition as in Example 1.

F(CF₂CF₂CF₂O)_(n)—C₂F₄—CONH—C₃H₆—Si(OC₂H₅)₃  (IV)

Dipping was followed by complete drying and heat treatment at 100° C.for 2 hours. The magnetic disk was coated (by dipping in the same manneras in Example 1) with a 0.001 wt % solution of the perfluoropolyethercompound (XI) expressed by the formula (XI) below in afluoride-containing solvent (“PF5052” from Sumitomo 3M Limited) underthe same condition as in

Example 1.

F(CF₂CF₂CF₂O)—C₂F₄—COO—⁺NH₃—C₆H₄—O—C₆H₅  (XI)

The lubricating layers in the data region and CSS region have athickness of 2.7 nm. The disk was tested for CSS characteristics andstiction characteristics in the same manner as in Example 1. The resultsare shown in Table 1.

Comparative Example 3

Example 1 was repeated to produce a magnetic disk by sputtering. Themagnetic disk was dipped in a 0.005 wt % solution of theperfluoropolyether compound (VI) expressed by the formula (VI) below(the same one as used in Example 1) in the same fluoride-containingsolvent as used in Example 1 under the same condition as in Example 1.

(C₂H₅O)₃Si—C₃H₆—NHCO—(CF₂CF₂O)_(m)—(CF₂O)_(n)—CONH—C₃H₆—Si(OC₂H₅)₃  (VI)

Dipping was followed by heat treatment at 110° C. for 2 hours. Theentire surface of the magnetic disk was washed with the samefluoride-containing solvent as above. Then, the magnetic disk was coated(by dipping in the same manner as in Example 1) with a 0.007 wt %solution of the perfluoropolyether compound (VII) expressed by theformula (VIII) below in the above-mentioned fluoride-containing solventunder the same condition as in Example 1.

F(CF₂CF₂CF₂—O)_(n)—C₂F₄—CH₂OH  (VIII)

The data region alone was washed with the same fluoride-containingsolvent as mentioned above. The lubricating layers in the data regionand CSS region have a thickness of 0.75 nm and 1.84 nm, respectively.The disk was tested for CSS characteristics and stiction characteristicsin the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 4

Example 1 was repeated to produce a magnetic disk by sputtering. Themagnetic disk was dipped in a 0.005 wt % solution of theperfluoropolyether compound (XIII) expressed by the formula (XIII) below(the same one as used in Example 3) in the same fluoride-containingsolvent as used in Example 1 under the same condition as in Example 1.

Dipping was followed by heat treatment at 110° C. for 2 hours. Theentire surface of the magnetic disk was washed with the samefluoride-containing solvent as above. Then, the magnetic disk was coated(by dipping in the same manner as in Example 3) with a 0.007 wt %solution of the perfluoropolyether compound (VII) expressed by theformula (VII) below in the above-mentioned fluoride-containing solventunder the same condition as in Example 3.

C₆H₅—O—C₆H₄—H₃N⁺—OCO—(CF₂CF₂O)_(m)—(CF₂O)_(n)—COO—⁺NH₃—C₆H₄—O—C₆H₅  (VII)

The lubricating layers in the data region and CSS region have athickness of 2.31 nm. The disk was tested for CSS characteristics andstiction characteristics in the same manner as in Example 1. The resultsare shown in Table 1.

Comparative Example 5

The magnetic disk prepared in Comparative Example 2 was mounted on thesame magnetic recording/reproducing device as used in Example 1. Theapparatus was deenergized during running, and the apparatus was allowedto stand for 24 hours. The magnetic disk could not restart due to strongstiction between the head slider and the disk in the data region wherethere is a large amount of weakly adsorbed lubricant.

What is claimed is:
 1. A magnetic disk, comprising: a substrate; amagnetic layer provided over said substrate; a protective layer providedover said magnetic layer; and a lubricating layer provided on saidprotective layer; wherein said magnetic disk comprises a CSS region onwhich a head slider is positioned when said magnetic disk starts andstops rotating and a data region over which the head slider ispositioned while said magnetic disk is rotating for recording orreproducing information on said data region; wherein said lubricatinglayer comprises at least a first lubricant and a second lubricant fixedto said protective layer, wherein said first lubricant is more firmlyfixed to said protective layer than said second lubricant and whereinsaid lubricating layer in said CSS region comprises not less than 10% ofsaid second lubricant and said lubricating layer in said data regioncomprises less than 10% of said second lubricant.
 2. The magnetic diskaccording to claim 1, wherein said first lubricant chemically reactswith said protective layer.
 3. The magnetic disk according to claim 1,wherein said lubricating layer includes at least one member selectedfrom the group consisting of perfluoropolyether compounds expressed bythe formulae (I) to (III) below, R₁—X—(CF₂CF₂O)_(m)—(CF₂O)_(n)—X—R₂  (I)F(CF₂CF₂CF₂—O)_(n)—C₂F₄—X—R₃  (II)F—(CF(CF₃)—CF₂—O)_(n)—CF(CF₃)—X—R₄  (III) wherein m and n are integers;R₁, R₂, R₃ and R₄ are hydrocarbon chains; and X is a divalent bindinggroup.
 4. The magnetic disk according to claim 1, wherein said firstlubricant includes at least one member selected from the groupconsisting of perfluoropolyether compounds expressed by the formulae(IV) and (VI) below,(C₂H₅O)₃Si—C₃H₆—NHCO—(CF₂CF₂O)_(m)—(CF₂O)_(n)—CONH—C₃H₆—Si(OC₂H₅)₃  (VI)F(CF₂CF₂CF₂—O)_(n)—C₂F₄—CONH—C₃H₆—Si(OC₂H₅)₃  (IV) and said secondlubricant includes at least one member selected from the groupconsisting of perfluoropolyether compounds expressed by the formulae(VIII) and (XI) below, F(CF₂CF₂CF₂—O)_(n)—C₂F₄—CH₂OH  (VIII)F(CF₂CF₂CF₂O)_(n)—C₂F₄—COO—⁺NH₃—C₆H₄—O—C₆H₅  (XI)  where m and n areintegers.
 5. The magnetic disk according to claim 1, wherein the CSSregion has a surface roughness greater than or equal to Ra 10 nm at theplace where the magnetic head slider is positioned when the magneticdisk starts and stops rotating, and the data region has a surfaceroughness smaller than or equal to Ra 3 mn at the place where themagnetic head slider is positioned while the magnetic disk is rotating.6. A method for producing a magnetic disk having a lubricating layer ona protective layer of the disk surface, a CSS region on which a headslider is positioned when the magnetic disk starts and stops rotatingand a data region over which the head is positioned and performsrecording and reproducing while the disk is rotating, comprising:carrying out the following steps (a), (b), and (c) in the data region;and carrying out the following steps (a) and (b) in the CSS region,where the steps (a), (b), and (c) are: (a): coating the disk surfacewith a lubricant (b): performing a heat treatment or UV treatment (c):washing the disk surface.
 7. The method for producing a magnetic diskaccording to claim 6, comprising the steps of: carrying out the steps(a), and (b), over all of the disk surface; and then carrying out thestep (a) over all the disk surface; and then carrying out the step onlyin the data region.
 8. The method for producing a magnetic diskaccording to claim 7, wherein, the lubricant which is first coated overall the disk surface comprises a compound selected from the groupconsisting of perfluoropolyether compounds expressed by the formula (IV)below, and F(CF₂CF₂CF₂—O)_(n)—C₂F₄—CONH—C₃H₆—Si(OC₂H₅)₃  (IV), and thelubricant that is secondly coated all over the disk surface comprises acompound selected from the group consisting of perfluoropolyethercompounds expressed by the formula (XI) belowF(CF₂CF₂CF₂O)_(n)—C₂F₄—COO—⁺NH₃—C₆H₄—O—C₆H₅  (XI)  where m and n areintegers.
 9. The method for producing a magnetic disk according to claim6, comprising carrying out the steps (a), (b), and (c) over all of thedisk surface; and then carrying out the step (a) over all of the disksurface; and then carrying out the step (c) and then (a) only in thedata region.
 10. The method for producing a magnetic disk according toclaim 9, wherein the lubricant that is first coated over all of the disksurface comprises a compound selected from the group consisting ofperfluoropolyether compounds expressed by the formula (VI) below,(C₂H₅O)₃Si—C₃H₆—NHCO—(CF₂CF₂O)_(m)—(CF₂O)_(n)—CONH—C₃H₆—Si(OC₂H₅)₃  (VI)the lubricant which is secondly coated over all of the disk surfacecomprises a compound selected from the group consisting ofperfluoropolyether compounds expressed by the formula (VIII) below, andF(CF₂CF₂CF₂—O)_(n)—C₂F₄—CH₂OH  (VIII) the lubricant that is thirdlycoated only in the data region comprises a compound selected from thegroup consisting of perfluoropolyether compounds expressed by theformula (VI) below(C₂H₅O)₃Si—C₃H₆—NHCO—(CF₂CF₂O)_(m)—(CF₂O)_(n)—CONH—C₃H₆—Si(OC₂H₅)₃  (VI) where m and n are integers.
 11. The method for producing a magneticdisk according to claim 6, comprising carrying out the steps (a), (b),and (c) over all of the disk surface; and then carrying out the step (a)over all of the disk surface; and then carrying out the steps (b) andthen (c) only in the data region.
 12. The method for producing amagnetic disk according to claim 1, wherein, the lubricant that is firstcoated over all of the disk surface comprises a compound selected fromthe group consisting of perfluoropolyether compounds expressed by theformula (XIII) below,

the lubricant that is secondly coated over all of the disk surfacecomprises a compound selected from the group consisting ofperfluoropolyether compounds expressed by the formula (VII) belowC₆H₅—O—C₆H₄—H₃N⁺—OCO—(CF₂CF₂O)_(m)—(CF₂O)_(n)—COO—⁺NH₃—C₆H₄—O—C₆H₅  (VII) where m and n are integers.
 13. The method for producing a magneticdisk according to claim 6, further comprising drying the lubricant inthe data region and the CSS region after the step (a).
 14. The methodfor producing a magnetic disk according to claim 6, wherein the CSSregion is formed to have a surface roughness greater than or equal to Ra10 nm at the place where the magnetic head slider is positioned when themagnetic disk starts and stops rotating, and the data region is formedto have a surface roughness smaller than or equal to Ra 3 nm at theplace where the magnetic head slider is positioned while the magneticdisk is rotating.
 15. The method for producing a magnetic disk accordingto claim 6, wherein the step (c) is carried out with a perfluorocarbonsolvent.